The invention relates to cordless electric devices. In particular, the invention relates to cordless electric devices powered by removable battery packs and to the manner of actuating the charge-discharge mode switch on such packs.
The availability of rechargeable batteries has lead to a variety of rechargeable battery-operated "cordless" devices including grass shears, hedge trimmers, toothbrushes, shrub trimmers, lawn mowers, flashlights, sprayers, screwdrivers, soldering irons, and the like. In some cases, the batteries are housed in a nonremovable pack. The recharging circuitry usually comprises a separate charging unit. In other cases, the charging circuitry is incorporated as a part of a rechargeable battery pack. It has also been previously proposed to provide a removable battery pack having its own recharging circuitry, the pack having AC type prongs and arranged so that the pack can be interconnected through the prongs to the device to be powered or through the same prongs to a household receptacle for recharging. It has also been suggested to have a removable rechargeable battery pack that could be connected to any one of several battery power consuming devices. A review of prior art practices with regard to battery pack powered devices is given in copending application, Ser. No. 607,376, and will not be repeated here.
The prior art practice was improved upon by the subject matter of copending application, Ser. No. 697,376, by providing cordless devices of a type which have a housing incorporating one or more pockets of unique construction adapted to receive one or more interchangeable battery packs. The battery pack is characterized by being in a rather rectangular flat box-like shape and having a pair of AC type prongs projecting from a position intermediate the length and width of one flat sidewall surface of the pack. These prongs are adapted to be received by a corresponding set of receptacle openings provided in the case plate member or, for recharging, to be received by an ordinary household receptacle supply. The switch in the battery pack unit of the prior invention comprises a double-pole, double-throw, spring-loaded switch which is incorporated as a part of an AC prong assembly which mounts both the AC prongs of the battery pack and the switch. This switch connects the rectifier means to the battery during recharging and is activated and spring-loaded by a fixed post member in the base of the pocket when the pack is installed and latched in its pocket to connect the prongs to the battery for discharge without requiring manual switching. Also, the switch spring causes the pack to tilt, i.e., to pop out, when unlatched. To facilitate uniformity in the pocket and insertion, retention and removal of the pack of the prior invention, the pocket in each device is provided with an outwardly opening receptacle formation at one end of the pocket whose perimeter is defined by a standardized pocket base plate having an inwardly inclined end so that the battery is inserted and removed by first assuming a tilted position on the base plate. When the battery pack is unlatched, it pops out and initially assumes such an outwardly tilted position. It is then withdrawn from the pocket by linear motion. During insertion, one end of the battery pack is first inserted in the receptacle formation in a tilted position and is then rocked about the inserted end of the pack, the receptacle formation insuring insertion of the prongs of the pack into the mentioned housing base plate receptacle of the device after which it is latched. The battery pack also includes a pair of spring contacts in the prong receiving receptacle of the device which makes both electrical and mechanical contact with the edges of the prongs being inserted and which insure both positive electrical and mechanical contact with the prongs. The mentioned switch spring in conjunction with these spring contacts causes the pack, when unlatched, to pop out as described. U.S. Pat. Nos. 3,370,475, 3,646,298 illustrate related trigger switches and it should be pointed out that all of the devices described in copending application, Ser. No. 607,376, require a separate electrical make-break switch on the device for starting and stopping the device. Such a switch is made necessary because when the pack is inserted in the pocket it is automatically placed in a discharge mode by the above-described fixed post member that contacts the spring-loaded switch. Thus, the device carries one electrical switch and the pack another. It is an object of the present invention to provide a tool design so that by actuating only the pack switch, power may be supplied to the load unit without the need for an intermediate electrical switch located on the device. By so doing, the battery pack switch is, in effect, being used as the electrical switch for the device and the electrical lead wires from the prong contacts may be directly connected to the load unit.